No. 433 .j SNAKES OF SOUTHERN MICHIGAN. 



or half plate occurs at the side between two gastrosteges. 

 This was the case in one female erythrogaster and in two males 

 and two females of sipedon. In all such cases the extra plate 

 has been counted as an additional gastrostege. 



5. Color. — In dealing with the matter of color, we meet 

 with great difficulties, owing to the impossibility of stating 

 differences with mathematical exactness. Moreover, in no 

 other particular is there so much room for difference of per- 

 sonal opinion and so many chances for errors of judgment. 

 Nevertheless, since it is in the matter of color that sipedon and 

 erythrogaster exhibit their most constant and striking differ- 

 ence, it is absolutely essential to any proper understanding of 

 the relation of the two forms that this difference be clearly 

 shown. First of all, therefore, an exact description of the 

 typical coloration of each form in life will be given, using 

 the color names of Ridgway's Nomenclature of Colors. 



Erythrogaster. Dorsal surface black, passing through slate 

 black and blackish slate to nearly slate color on sides ; ventral 

 surface bright rufous, orange rufous, or even Chinese orange, 

 shading anteriorly through saturn red to deep chrome on the 

 throat and finally to creamy white on the chin ; whole head 

 with a reddish tinge ; upper labials nearly rufous except on 

 upper and anterior edges ; outer, anterior edges of gastrosteges 

 more or less slate color, the same shade being more or less 

 evident on urosteges. 



Sipedon. Dorsal surface dark bister with irregular, narrow, 

 transverse bands of wood brown ; beginning on the fifth or 

 sixth row of scales, and running down vertically on sides, are 

 broad, pale, almost whitish bands, anteriorly and posteriorly 

 continuous with, but for the most part alternating with, the 

 transverse bands on back ; between these vertical lateral bands 

 the scales are chocolate brown, more or less mottled with black ; 

 chin creamy white ; gastrosteges creamy white, anteriorly with 

 two semicircular spots of hazel or ferruginous, the arc of the 

 semicircle coincident with the anterior edge of gastrostege ; 

 farther back additional ferruginous spots appear, and these 

 gradually merge together, at the same time becoming more 

 and more clouded with black, so that near the vent the 



